We're always eager to get in the garden come spring. What's different this year is that spring came earlier than usual, so there are lots of chores you can tackle now. But you'd be wise to wait to plant most annuals and perennials.
Some years, March comes in like a lion and goes out like a lamb. This year, it went out like a tropical lemur. With temperatures approaching 80 degrees for several days (In March? In Minne-snow-ta?), giddy gardeners have been itching to push the season.
Resist the urge. Just because it felt like summer for a few blissful days, that doesn't mean plants should go into the ground any sooner than the usual recommended dates for Zone 4. Frost-tolerant vegetables such as lettuce, cabbage and broccoli can be safely planted as soon as the soil can be worked (which, for many local gardeners, was in very early April this year).
But warm-season veggies, such as tomatoes, peppers and eggplant, need warmer soil and air to thrive, and are best planted in late May. The same goes for most flowering annuals and perennials. You'll risk your investment if you plant before May 15 (the estimated frost-free date in the Twin Cities).
"The problem is, we can still go through a freeze," said Jeff Gillman, associate professor of horticulture at the University of Minnesota. "If people plant early because they're all excited about the warm weather, they could lose plants. Changing your planting dates now is asking for it."
That said, there are plenty of lawn and garden chores you can tackle right now:
• Clean out the garden. Cut perennials to the ground and use a lightweight rake to remove winter mulch, debris and dead plant material.
• Improve your soil. Adding organic material (compost, peat moss, aged manure) now is an investment in better results later.
• If you haven't been composting, why not start? "People think it's really, really difficult, and it's really, really easy," Gillman said. "All it is is a bed of dead plant material that's allowed to rot. As long as you turn it every two or three weeks, there's nothing else you need to do."
Buying a commercial compost bin is probably the easiest way to get started. Kitchen scraps, grass clippings, dead plants and weeds are all good compost fodder. (But don't add meat scraps, which can attract rats, Gillman said. "Be careful composting any animal material.")
If you don't want to make your own compost, Gillman recommends buying compost, putting a 1- to 2-inch layer on top of your beds, and tilling it into the ground. (Bagged compost is preferable to buying it from a pile, he said, because it is more likely to have undergone a quality-control process and is less likely to harbor diseases.)
• Spread a thin layer of organic material on the dirt around your emerging perennial plants. Mulch, which ultimately turns into compost, is a no-till way to add organic material to your soil, Gillman said. He recommends wood or bark chips, or straw. "Hay has seeds, which you don't want," he said. Another option: Add a layer of compost, then put mulch on top of that, a method called "lasagna gardening."
• Prune summer-flowering shrubs that bloom on new wood (such as some hydrangeas, shrub roses and spireas).
• Design a rain garden, which captures the water that runs off from your house. Or buy or build a rain barrel to capture runoff from your gutters. (For information on getting started and tips, visit www.metroblooms.org or www.bluethumb.org.)
• Plan your garden. If you want to join the crowd growing veggies this season, plan your plot so those veggies can hog the sunlight. "Pick the sunniest spot you've got," Gillman said. And consider rotating your crops, so you're not growing the same vegetable plants in the same soil, year after year.
If you're one of the many gardeners who intend to grow vegetables in containers this season, make sure your soil is up to the challenge. Container-grown tomatoes, for example, are vulnerable to calcium deficiency, which can result in an unappetizing condition known as "end rot," Gillman said. He recommends adding gypsum or crushed eggshells (two or three per plant).
• Prune spring-blooming shrubs, such as lilacs, azaleas and forsythia, until they're done blooming. If you prune now, you'll remove this year's flowers.
• Water and fertilize ornamental trees and shrubs. (That should be done in early May.)
• Plant small trees and shrubs. (May is good because it's usually neither too hot nor too cold, and soil tends to be moist.)
• Divide and transplant perennials, such as hostas and daylilies. (Soil should be warm and dry, which usually doesn't happen until early to mid-May.)
• Fill your containers and beds with tender annuals and warm-season vegetables. (Usually mid-May, although some frost-tolerant blooms, such as pansies, can be planted weeks earlier.)
• Rake the lawn.
• Seed bare or thin spots to encourage thicker growth and deter weeds.
• Aerate (if you haven't done so in a couple of years). It will help the grass absorb water and nutrients.
• Fertilize, after you've mowed once or twice. Thanks to our unseasonably warm late March and early April, grass is already actively growing and is about two weeks ahead of schedule, according to Bob Mugaas, an extension educator with the University of Minnesota. If current weather trends continue, that'll push all lawn chores (mowing, fertilizing and weed control) ahead of schedule, as well. "Pay attention to what the grass is doing," Mugaas said.
• If you fertilized in the fall, skip it this spring.
• Let the grass grow longer, to encourage deeper roots (2 1/2 to 3 1/2 inches). This will help your lawn tough it out during hot, dry weather.
• Leave grass clippings on the lawn. They add nutrients to the soil.
Japanese beetles, voracious pests that have been driving gardeners buggy in recent years, will continue to plague us this growing season. "They definitely have been increasing the last four or five years," said Jeff Hahn, entomologist at the University of Minnesota. The beetles are a metallic green/bronze color, and they turn plants into lace doilies, chomping through the leaves and leaving the veins behind.
"Part of what makes them challenging is that they feed on over 300 plants," including roses, grapes, raspberries and lindens, Hahn said. If you endured some munching last year, but your infestation wasn't extreme, he recommends handpicking the beetles off your plants once they start to appear, usually in late June or early July. "The best time is the late afternoon," he said. "They do their active feeding at night." Then, "throw them into a bucket of soapy water," he said. That will kill the beetles, but if you knock them off your plants without killing them, they will just fly back.
If you want to deter Japanese beetles without killing them, consider a low-impact, botanical-based insecticide, such as Neem, Hahn said. "It prevents them from feeding. They will move on." If stronger measures are called for, you can treat your soil with an insecticide containing imidacloprid, Hahn said. The best time to apply is in May, before beetles lay their eggs. Make sure that the plants you want to treat are listed on the insecticide label, he said.
The beetles' white grubs do feed on plant roots, but Hahn doesn't recommend treating them. "If you have damage from grubs, concentrate on treating the adults," he said.
Oak trees also will be under siege this season, thanks to the two-lined chestnut borer, Hahn said. The beetle attacks unhealthy oaks, burrowing under their bark. Drought conditions in recent years have left oaks vulnerable to this pest. If you have an oak tree, make sure it's well watered, to maintain its vigor.
Kim Palmer • 612-673-4784